1. Field of the Invention
The present invention relates to a gasket clamp structure used for clamping a gasket between a casing and a retaining member in various apparatus, such as an automatic transmission system.
2. Description of the Prior Art
A known example of the above type of gasket clamp structure is illustrated in FIG. 3. This structure includes a gasket clamping bolt 30 having a male screw 31 and a coating material 32 that is applied to an outer circumferential surface of a distal end portion of the male screw 31, and retaining member 33 and gasket 34 having respective mounting holes 33a, 34a. The gasket clamping bolt 30 is passed through the mounting holes 33a, 34a of the retaining member 33 and gasket 34, and screwed into a thread hole 36 of a casing 35, so that the gasket 34 is clamped between the casing 35 and the retaining member 33.
In the known structure as described above, however, when the male screw 31 of the gasket clamping bolt 30 is brought into engagement with a female screw 36a formed in the thread hole 36, through the mounting holes 33a, 34a of the retaining member 33 and gasket 34, and screwed into the thread hole 36 so as to clamp the gasket 34, as shown in FIG. 3, the radially inner face of the mounting hole 34a of the gasket 34a engages with thread grooves of the male screw 31 of the bolt 30, and scrapes the coating material 32 off the thread grooves, as shown in FIG. 4. At the same time, the female screw 36a of the casing 35 scrapes the coating material 32 at around the opening or inlet of the thread hole 36. As a result, scrapings or flakes 32A of the coating material 32 are deposited on the opposite major surfaces (seal surfaces) of the gasket 34, as shown in FIG. 4, and consequently the gasket 34 may not be able to provide a sufficient seal, thus causing leakage of oil or the air.